The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Moving Picture Experts Group (MPEG) and Video Coding Experts Group (VCEG) together stepped ahead of the existing MPEG-4 Part 2 and H.263 standard methods to develop a better and more excellent video compression technology. The new standard is called H.264/AVC (Advanced Video Coding) and was released simultaneously as MPEG-4 Part 10 AVC and ITU-T Recommendation H.264. H.264/AVC (hereinafter, referred to as “H.264”) has promoted great development to improved picture quality and performance by using various encoding methods. Further, there is ongoing standardization meeting for the new standard covering picture quality in a high-definition (HD) level or more by a joint team of MPEG and VCEG called Joint Collaborative Team on Video Coding (JCT-VC).
A video encoding method divides an input image in units of blocks and predicts each block by subblock sizes according to an inter-prediction mode or an intra-prediction mode to generate a residual block, subjects the generated residual block to an integer transform designed based on a Discrete Cosine Transform (DCT) in units of 4×4 or 8×8 blocks to generate a transform coefficient, and then quantizes the transform coefficient according to a given Quantization Parameter (QP). Further, a blocking effect generated due to the transform process and the quantization process is reduced through loop filtering.
The inventor(s) has noted that to increase accuracy of a motion compensation performed in H.264/AVC, a method of finding a more accurate motion vector is used by searching for the motion vector not only in an integer sample having an integer pixel but also in the position of up to a sub sample having a resolution of a ⅛ sample in case of a luminance (luma) component.
The inventor(s) has experienced that fixed block sizes disable accurate predictions and compensations on pixels changing due to various motions across images, resulting in a decreased video encoding efficiency. That is, in predicting and compensating for various video motions such as zoom in and out, shaking, panning, rotation and the like, the inventor(s) has experienced that predictions would be efficiently performed with various shapes and sizes of blocks other than a 4×4 block size or a 8×8 block size. The inventor(s) has, however, experienced that the prediction and compensation method using fixedly sized blocks cannot encode videos adaptively to the video characteristics, thereby deteriorating the encoding efficiency.